The instant invention relates, generally, to the masonry block industry, and, more specifically, to a device and a method for producing a masonry block having a portion or all of its outwardly facing exterior surface of a textured nature.
The concept of creating a masonry block surface having a texture different than the flat, molded surface common in masonry, or concrete, blocks, is well known. Various techniques have been used to enhance masonry product appearance by creating, in some fashion, a textured surface, for more than a century. There are two generally accepted methods of creating a textured masonry surface. The surface can be created after the unit has been cured, known as “hard-split” or, the surface may be textured before the unit has cured, in a process sometimes known within the industry as “green-texturing.”
The “hard-split” technique is well known, but has distinct disadvantages. The technique is costly, requiring the use of an expensive knife splitter, and an operator to constantly oversee the process. Such a technique also invariably slows down the production process and, inevitably, produces waste as the units are split. Because the units are cured, as of the split, the excess material is not re-utilized, and must be discarded. Further, the “hard-split” process is generally useful only in producing straight splits, and is difficult to utilize in a radial style split, without a great deal of modification effort and additional cost.
The process generally described a “green-texturing,” was developed in an attempt to answer the high costs of labor and equipment by definition entailed in the “hard-split” process. A number of processes have previously been developed to attempt to address these problems. “Green-splitting” can occur in a number of methods, but may generally be classified into two categories, to wit: either texturing after the unit is discharged, outside of the mold and still in a “green” or plastic state, and texturing which is done within the mold, or by the very process of discharging the unit from the mold. Several earlier patents suggest processes which create a textured block surface after the block has been removed or stripped from the mold but before the block has been cured. In this “green” or uncured state (sometimes referred to within the industry as a “plastic” state—that is capable of being molded or receiving form), great care must be utilized in removing the unit from the mold, so as not to disturb the unit, in its fragile, plastic state, prior to curing outside of the mold. Although limited textures may clearly be applied utilizing these techniques, they require significant maintenance, and are limited in the amount of texture which may be added. Regular attention and maintenance are additionally required, to attempt to minimize the number of units that need be discarded because of improper texturing, or disintegration of the unit itself.
U.S. Pat. No. 3,981,953, to Haines, discloses a process whereby texture is applied within the mold, but only to the top or horizontal surface. Applying texture to the top surface limits the use of such a texturing process where the masonry units involved have connective or other features on the top and/or bottom surface which contribute to the functionality of the unit. Further, rods which hold material within the mold may leave marks in the unit detracting from its overall aesthetic appearance. The processes involved in the '953 patent allow for adaptation to a vertical surface, but not without significant effort and, likely, production problems.
U.S. Pat. No. 5,078,940, and U.S. Pat. No. 5,217,630, both to Sayles, are directed to solutions to the problems referenced above as being associated with former methods, as they create a textural vertical surface within the mold cavity. However, because material is retained within the mold between molding cycles, a cleaning problem is created wherein material must be removed, or voided out, in a separate step, on a regular basis. With regard to the '630 patent, another disadvantage is that, as material breaks away, there in an inclination to create an angled feature of the vertical face from top to bottom. While this may not be a significant disadvantage in very short units, such as those used for retaining walls, the textured portion of the block creating an angled face can cause significant problems in units having a longer vertical face and will likely preclude use for exterior surfaces on architectural building projects. Such a process also produces waste on the production pallet which must be removed in a separate operation.
U.S. Pat. No. 6,224,815, to LaCroix, et al, addresses the issue of cleaning away excess material created in the texturing process, as it provides a self-cleaning function when the supporting pallet comes in conjunction with the mold and its operating means. The process involved in the '815 patent utilizes a metal grate suspended between two units within the mold. The grate is suspended between two areas of compacted materials, so that, with each cycle, two units are produced. However, either an even number of units must be produced or a large amount of waste is produced by each cycle if the optimum layout contains an odd number of units. There may also be waste extruded or dropped onto the production pallet. Further, streaks may develop in the finished product utilizing the process described in the '815 patent, as materials trapped within the open parts of the grates can smear against the upper face of the units.
U.S. Pat. No. 3,940,229, to Hutton, U.S. Pat. No. 5,879,603, to Sievert, and U.S. Pat. No. 6,209,848, to Bolles, et al, all disclose variations of what may be described as a “lip” system. As disclosed in the '229 and '848 patents, a single lip or striker at the bottom of the mold strips the material from the face of the unit as the unit is discharged. The '603 patent discloses a two lip system, one at the bottom of the mold and one at the top of the compacted unit. Both the device of the '848 patent and that of the '229 patent still tend to force materials to “smear” on the upper portion of the units, particularly units of greater height, as sufficient room is not allocated within the block itself to receive material which has been stripped or accordingly removed by the striker or “lip” as it pulls material away from the unit creating the textured surface below. The '603 patent retains material within the mold between the upper and lower lip similar to that of the process disclosed by the '603 patent, but, as is the case with the '229 and '848 patents, this process also may create a material smear on the upper portions of units of any significant height. All processes disclosed by the referenced prior art tend to leave material on the production pallet.
The problems generally associated with the existing art in “green-texturing” techniques, in the way of leaving “green” material on the pallet or supporting platform, the requirement of regular cleaning of the mold, textured face surfaces which are angled or substantially deviated from the vertical, particularly in taller units, and smudged or smeared material on units beyond those of minimum height, are all results of the reaction which takes place when material is torn away from the “green textured” unit surface when the material is forced out of the mold, or a scraper or striker unit or bar extends into or moves against a significant portion of the unit surface. An overlaying or smearing effect which is prevalent in many of the applications of the prior art, is produced when material moves only in a vertical direction, and compounds upon itself or is left within the mold when the masonry unit is discharged. The prior art does not disclose any satisfactory method for disposition of excess material without retaining it within the mold enclosure or upon the pallet or support plate below the mold. As is evident, the prior art provides only for continued movement of material vertically against the face of the masonry unit.
Accordingly, a need exists for a mold device and method which allows displacement and movement of excess material produced during the process, during each cycle of manufacture of units, and, in so doing, creates an opportunity for, and forces, lateral as well as vertical movement of such material. It is an intended feature of the instant device and method, to eliminate the problems associated with the prior art, as set forth above and, in so doing, to produce a random and rough texture on the masonry unit, without a smearing effect, and without leaving substantial excess material within the unit, or upon the supporting platform.
The present invention is further addressed to a need, as is evident from a review of the prior art, for a device and process which may be used on surfaces for retaining wall units, architectural masonry units, paving units and any number of other masonry products which are molded and for which an exterior textured surface is desirable.